Rheostat mounting



Nov. 3, 1936. N. c. SCHELLENGER I 2,059,313

RHEOSTAT MOUNTING Filed May I L5, 1935 I 3 Sheets-Sheet l Inventor; Newton 6? jcfzellegaen NOV. 3, 1936. SCHELLENGER 2,059,813

RHEOSTAT MOUNTING Filed May 15, 1933 3 Sheets-Sheet 2 Nezwm' 6. 5C/Z6ZZ87Z er Patented Nov. 3, 1936 PATENT OFFICE RHEOSTAT MOUNTING Newton 0. Schellenger, Elkhart, Ind., assignor to Chicago Telephone Supply Company, a corporation of Indiana Application May 15, 1933, Serial No. 671,031

5 Claims.

My invention relates to an electrical circuit control device and more particularly relates to a variable resistance device of the type employed in tone control and volume control apparatus of radios and other sound transmission systems, and including a resistance element mounted within a housing and having a contact element engageable therewith to vary the resistance in a circuit or circuits to which the resistance element is connected.

Heretofore, variable resistance devices such as rheostats have been mounted on panels by a single hole type of mounting wherein a journal bushing is threaded exteriorly at one .end which end enters a suitable hole in the panel and then a nut is inserted upon the threaded bushing to hold the device in place. Such devices have, also, been held in position by screws or rivets and bolts passing through the holding panel and the base of the device. Disadvantages presented by the above types of mounting are cost, utilization of valuable space, time required for mounting, requirement for extra parts'where a single hole type of mounting is employed to prevent rotation 5 of the rheostat relative to the panel, and a poor bearing unless the bushing is long.

It is, therefore, an object of my invention to provide a rheostat housing comprising among other features a bearing or bearings for an operating shaft, and said housing being provided with extending projections or cars for firmly securing the rheostat or similar control device to a panel, or other surface to which it may be connected.

A further object is to provide a rheostat housing having a plurality of aligned bearings for the operating shaft therein, whereby any wobbling of the operating shaft is prevented.

It is a further object of this invention to provide an electrical control housing having bearings formed therein in such a manner as to present a maximum rigidity with a minimum thickness of material.

A further object is to provide a variable resistance device having an operating shaft to which a contactor arm may be rigidly attached in an insulated manner, without the aid of any additional fastening elements such as, a spline, set-screw, rivet or bolt, etc.

It is another object of this invention to provide a variable resistance control device of greatly simplified construction with a minimum number of parts and with the partsarranged in a housing in such a manner as to reduce the number of operations necessary in the manufacturing and assembling of the device.

A still further object of this invention is to construct an improved variable resistance control device, that may be easily and economically produced, which is rugged in construction and has a maximum efilciency and accuracy of oper- 5 ation.

Still further advantages of the invention will become evident by reference to the following detailed description taken in connection with the accompanying drawings of certain specific em- 10 bodiments thereof, the scope of the invention being limited only by the terms of the appended claims.

Figure 1 is a perspective view of a variable resistance control device constructed in accordance with my invention;

Figure 2 is a perspective view of the variable resistance control device shown in Figure 1 taken from another position thereof;

Figure 3 is a sectional view of the variable resistance control device with the shaft thereof shown partially in. elevation and particularly showing the bearings for the shaft and the panel mounting ears;

Figure 4 is a perspective view of the variable resistance control device showing the same mounted on a panel and with the mounting ears of the casing thereof clinched in place;

Figure 5 is a sectional view of a modified form of variable resistance control device embodying my invention and showing the panel in spaced relationship therewith;

Figure 6 is a perspective view of the modified form of variable resistance control device shown in Fig. 5 united to the panel;

Figure? is an enlarged fragmentary perspective view, showing the construction of the housing of the modified form of variable resistance device shown in Fig. 5;

Figure 8 is an enlarged fragmentary sectional view showing the positioning insulator mounted on the shaft;

Figure 9 is an enlarged fragmentary sectional view of the .end of the operating shaft and showing the relationship thereof to its associated bearing;

Figure 10 is an enlarged fragmentary elevational view of the plate and shaft assembly;

Figure 11 is a perspective view of the insulation strip adapted for use between the plate 50 and the shaft;

Figure 12 is a fragmentary sectional view of the contactor arm assembly; and,

Figure 13 ls a plan view of the contactor arm assembly.

Referring now in detail to the drawings, particularly to Figures 1, 2, and 3, the metallic housing of the variable resistance control device is generally indicated by A. The housing A has a front plane face ill from which an integral cylindrical wall l2 extends, thus forming a cupshaped portion of the housing A, and from the free end of the cylindrical wall protrude a plurality of bosses or struck out portions H. The details of the bosses H are not of the essence of the present invention, the structure shown being taken from my co-pending application, Serial No. 577,624, flied November 27, 1931, and shown here by way of example only. A front hearing it is formed substantially in the center of and integrally with the front face In and is obtained by drawing a cylindrical hub H in a direction opposite to that in which the wall 12 extends. Also, struck or stamped from the front face but remaining integral therewith are a plurality of panel mounting ears l8, I9, 20, and 2!, of predetermined length, which ears project substantially at right angles to the front face and in line with the cylindrical wall l2. The mounting ears ll, I9, 20, and 2| are adapted to extend through openings 64, 66, 68, and 10 of a supporting panel 80 and be bent over against the surface of said panel to securely fix the housing to the panel.

A rear face or cover 22 has at its periphery a flange 24, and integral with the flange are a plurality of tongues 26 adapted to engage or clinch over the aligned bosses I! on the cylindrical wall I2. An annular hub or bearing 28 protruding or thrust out of the rear face 22 in axial alignment with the front face bearing 5 thus provides a second bearing for an operating shaft, generally designated B.

As the hereinbefore described structure is primarily formed in punch presses, the use of suitably formed dies in stamping out the bearings causes the bearing surfaces to be hardened and smooth, thus insuring an accurate fltting and a long life.

The operating shaft B, of suitable length, has a main cylindrical body 30 and has at one end of the body a reduced cylindrical journal 32. A thrust bearing or shoulder H is provided on the shaft partly overlying the reduced journal 32. The shaft also carries a rigid plate J adapted to exert a thrust against a washer 38 and a positionlng tube 40 through engagement with a contactor spring ring 42, and the tube 40 in turn bears against the inside of the front face H) of the casing A adjacent the front bearing I8. Thus, movement of the shaft B is limited in an axial direction by the thrust bearing or shoulder at on the shaft bearing against the rear face 22 when the shaft is pushed in and by the plate 3 on the shaft engaging against the contactor spring ring 42, an insulating washer 38 and the positioning tube 40 which tube in turn engages the inside surface of the front face It adjacent the front bearing I when the shaft is pulled out.

Mounted upon the plate J, see Figs. 3, 12, and 13, is a resilient removable contact member H" adapted to electrically engage a resistance element ll, which element comprises an insulating strip'wound with wire or coated with any suitable conducting material.

As shown in Figs. 12 and 13, the contact mem-- ber "H" has generally a -U-shaped formation in plan view. The flexible portions of the contact member, each of which is comprised of sections 4| and u, are substantially parallel and supported in such manner that they will bend without twisting or warping and thereby the maximum range of flexure for a given thickness and kind of arm is obtained. Twisting of the parallel legs 44 and their extensions ll is prevented by the bight section 43, which is formed at a substantial 6 angle to the legs 44. This angularity provides section 43 with great rigidity and practically eliminates any drooping of its ends with respect to its center portion, due to the pressure of the legs 44 being in one direction and the pressure exerted by the contactor portion being in the other direction. If this drooping occurred to any appreciable extent, the legs 44 would be twisted from their normal position and their flexibility greatly impaired.

When the shaft B, the plate J, the insulator 8i and the arm H are removed from the rheostat casing, the arm H may easily be removed from the assembly by simply disengaging each ear I which extends from each of the legs 44, and removing the extensions 4| from the notches l3 and 39 in the plate J. It is obvious that the arm may be replaced without any machine operations. Another important function of the slot II in the plate 36 and the arm extension 4| is to determine the pressure of the contactor 45 on the resistance element. This may readily be understood by reference to the arm H shown in dotted lines on Fig. 12,, which represents the position the arm tends to take before flexed into position on the resistance element. The angle of this free position of the contact member H to the plane of the plate J is therefore determined by the ratio of the length of the slot to the thickness of the arm. Obviously, the angle between the plate and the free position of the arm will be greater, as will the pressure of the contacting section II against the winding (assuming no change in the arm) if the slot is short and the arm thick than if the plate were thin and the slot of greater length. The relative pressure of the resistance element and the contactor II when the arm is in position causes a pressure to be exerted by the arm against the corners 3| formed by the notch in the plate, which corners act as a fulcrum, and also a pressure on the opposite corners 35 of the same notches 39 by the extension ll of the legs 44. These pressure reactions cause a flexing of the legs I and their extensions 4! so that a considerable range of flexibility is obtained. The arrangement of the arm and plate for securing the necessary contact pressure without forming that portion of the arm that is relied upon for obtaining the necessary flexibility, is a great advantage, as it allows a much more uniform contact pressure to be obtained when large quantities of rheostats are to be produced. The lack of uniformity, when such forming operations are employed, is due. to the fact that the forming operations are subject to wide variations from uneven blows of the machine in which the operation is performed, and also to wear on the forming die. A forming operation further exaggerates the variation in pressure due to the thickness of the contact am. All of these variations are eliminated with my construction.

Further advantages of my arrangement are that it allows a greater range of movement without causing the arm to be permanently deformed. gives a greater life to the spring, and gives the 70 arm greater resistance to buckling and warping as a whole.

Ears 41 on the arm engage notches 33 in the plate J to prevent relative movement of the plate and arm as a whole.

The projection 31 on the plate J is adapted to engage the rivet GI and is of such width as to limit the arm rotation to the desired amount.

To insulate the resistance element 46 from the front face I0 of the housing, and, also, to prevent the entry of dust or foreign particles into the unit, an insulating gasket 50 is placed against the outer portion of the front face I0 but within the housing, so that the gasket will overlie and close the spaces defined by the striking out of the panel engaging ears I8, I9, 20, and 2|. An insulating strip 52 is placed around the inner periphery of the cylindrical or circular wall I2 to insulate the resistance element 46 from the cylindrical wall of the housing.

The plate J is secured in non-rotatable position on the shaft by serrations or teeth around the inside of the flange 54, biting deeply into an insulating strip 55 of paper, fibre, bakellte or other suitable material, see Figs. 9 and 10. This strip 55 is also in close engagement with the shaft through the medium of teeth 56 on the shaft which are created by knurling, or in any other satisfactory manner. I provide this assembly in a very economical and eflicient manner by utilizing a flat strip of fibre, such as shown in Fig. 11, which is formed into a cylinder of a diameter greater than the serrated interior of the flange 54. This cylindrical strip is then subjected to great pressure so as to reduce its outside diameter, and then forced into the flange. Forcing this strip into the flange the fibre lined fiange, has teeth 56 around its surface through one portion. These teeth are preferably created by knurling so that the valleys are below the normal shaft surface and the peaks above. The shaft is then forced into the fibre cylinder under considerable pressure, so that the fibre fills in the spaces between the teeth. By making the assembly in this manner, the fibre is maintained under pressure great enough to prevent any opening occurring at the point 6| where the ends of the piece 55 abut.

Where a grounded shaft is desired, a plurality of axial serrations 56, see Fig. 5, may be cut upon the end of the shaft wherein the conductive supporting plate is inserted and the supporting plate hub forced upon the shaft.

A panel 60 upon which the rheostat is to be mounted is provided with a hole 62 of sufiicient size to accommodate the hub or bearing I6 and, also, is provided with suitably spaced smaller holes 54, 65, 68, and 10 adapted for registration with the ears I8, I9, 20, and 2I of the housing. To secure the rheostat to the panel the rheostat is held against the panel so the ears I8, I9, 20, and 2I register with the holes 64, 66, 68, and 10, and the ears are then bent to grip the panel, either by a hand press or a kick-press". Thus, an operation which is simple, expeditious, positive and accurate may be performed by employing my invention. The arrangement for retaining the variable resistance device in a supporting member by means of cooperating ears and openings is disclosed in the copending application of Newton C. Schellenger and Mervin B. Arisman, Serial No. 697,718.

It will be observed by referring to Fig. 4, that the type of mounting hereinbefore described prevents angular motion of the rheostat, as well as axial motion, relative to the panel 60 and it will be found that vibration will not readily loosen the device.

Suitable terminals are provided for the resistance element and the type disclosed in my copending application, Serial No. 602,007, filed March 30, 1932, may readily be employed.

A modified rheostat housing particularly embracing a panel mounting arrangement and shaft bearings is shown in Fig. 5.

A base or cover member, generally designated F, carries a planar resistance element I00 and suitable terminals for making electrical connections with the resistance element. A detailed description of the terminal arrangement for this type of resistance element may be obtained from my co-pending application, Serial No. 668,757, filed May 1, 1933.

A contacting member I04 in electrical contact with the resistance element is engaged by a rotatable arm I06, which arm in turn is securely attached to an operating shaft I08 by any suitable means, but by way of illustration a plate H0 is employed. It is, of course, obvious that any other desired resistance contacting arrangement might be used. As hereinbefore described in connection with Figure 3, the shaft is limited in axial movement, although it is to be noted that in Fig. 5 the positioning tube is eliminated.

A front bearing II2 for the shaft is formed in the base F by punching or drilling a hole therethrough of a suitable diameter.

A metallic cup-shaped housing, generally designated E, has a face H4 and a cylindrical wall IIG open at one end. A bearing H8 is extruded, as by stamping, and formed integrally with the rear plane face II4.

A plurality of symmetrically positioned projections at the open end of the housing or casing E slid over the end of the shaft I08 into position so that the insulating strip H1 is engaged by both the base F and the housing E. The housing is then maintained in the proper relation to the base by bending into holding engagement on the base the shorter ears I20 and I 22 of the cupshaped housing.

The insulating strip II'I thus spaces the two essential members of the enclosure by a predetermined amount, closes the opening in the housing over the terminals, provides adequate insulation between members of the rheostat and the housing, and makes the seal between the base E and housing F substantially dust proof. The same general arrangement is shown in my co-pending application, Serial No. 518,281, filed February 25, 1931. In cases where space will permit, it may be desirable to use a metal member instead of an insulating member for the purpose of spacing the housing and base members apart.

A panel G, upon which the rheostat is to be mounted, is provided with suitably positioned holes, one of which will accommodate the shaft and the remainder of which will register with the tongues I24. Thus, by-placing the shaft through the central opening of the panel and clinching the tongues I24 in clamping engagement with the panel, it will be observed that the shoulder sections I26 and I28 bear against the panel adjacent the respective holes through which the tongues I24 protrude.

The shoulders I26 and I28 space the base F away from the panel G to provide suflicient clearance between the panel and the current-carrying parts carried by the base, so that in the event a metal panel is used, there will be no danger of short circuits or grounding any current-carrying parts of the rheostat.

A modified arrangement of a plate mounted upon an operating shaft wherein the plate is adapted to carry a contactor arm and positioning structure is shown in Figure 8.

An operatingshaft 200 is journaled on a large diameter bearing 202 and a small diameter bearing 204. The bearings 202 and 204 are drawn from faces 206 of the cover member, and 208 of the base member respectively. An insulating cylindrical member 210 of suitable length, and formed from a flat piece of insulating material, is inserted upon one end of the operating shaft, and upon the outer surface of that tube is forced a flange 2 of the plate 2l2. A spring conductor ring 2l6 is positioned adjacent the plate 2, which plate is of the same structural details as the plate 36, Fig. 12, and the plate H0, Fig. 5, and the ring is mounted upon an insulating washer 2l6. The washer H8 is suitably positioned from the inner surface of the face 206 by a positioning tube 220. It is to be particularly observed that the tube 210 is of such length that any axial thrust permits the adjacent tube edge to engage the internal surface of either the face 206 or 208, and, also, that the shaft 200 is insulated from the contactor arm.

Although the invention has been described in considerable detail, such description is intended as illustrative rather than limiting, as the invention may be variously embodied, and the scope of the invention is to be determined as claimed.

I claim:--

1. A variable resistance device comprising a plurality of housing members having integral bearings therein, a shaft Journaled in said bearings, a resistance element, a contactor engageable with said resistance element, an actuator for said contactor mounted on said shaft, an insulating bushing extending between said housing members to space them relative to each other, said bushing being disposed to insulate said actuator from said shaft.

2. A variable resistance device comprising a housing, a resistance element within said housing, a shaft journalled in said housing, an actuator mounted on said shaft having eccentrically 10- cated coupling elements thereon, and a contactor having complementary coupling elements in engagement with the coupling elements on said actuator to constitute a separable coupling, said coupling flexing said contactor upon said resistance element against the spring tension thereof.

3. In a variable resistor, an arcuate resistance element, a shaft concentrically mounted with respect to said element, a contactor arm associated with said shaft in engagement with said element, an actuator connected to said shaft having eccentrically located spaced bearings for mounting said arm, said arm being sprung from its normal position by said bearings to exert a predetermined contact pressure upon said element.

4. A variable resistance device comprising a housing, a resistance element in said housing, a shaft extending through one wall of said housing and positioned against a thrust bearing in another wall of said housing, a contactor engageable with said element, a conductive actuator secured to said shaft, insulated from the shaft and electrically connected to said contactor for transmitting motion thereto, and a resilient brush bearing against said actuator to establish electrical contact therewith and against said first wall to urge said shaft axially against said thrust bearing.

5. A variable resistance device comprising a housing having a plurality of parallel walls, a shaft journalled in one of said walls and bearing against another of said walls, a resistance element in said housing, a contactor engageable with said resistance element, an actuator rigidly secured to said shaft for imparting motion to said contactor, means for retaining said shaft against axial movement comprising an insulating washer having a spring tensioned brush mounted thereon, said brush pressing against said actuator to effect electrical connection therewith.

NEWTON C. SCHELLENGER. 

